Our original P01 grant application was motivated by the remarkable differences in health care intensity in the US. In this resubmission, we sharpen our focus in three ways. The goal is to understand and improve efficiency, the target is a more actionable level for physicians and the hospitals where they work, and the means include collaborations with key stakeholders to design successful interventions. The projects are: 1. Measuring the Efficiency of Health Care Providers. This project develops measures of efficiency - both quality and costs - and explores their implications at the level of primary care physicians, physician groups, and hospitals. We use Medicare data, patient and physician surveys, and specialty board certification scores from the American Board of Internal Medicine and the American Board of Family Practice. 2. Causes and Consequences of Variation in Pharmacotherapy Efficiency. We describe and model variation in prescription drug use using longitudinal claims data from very large insurance providers in two states, studying both consequences of variation in prescription drug use in outcomes and the impact of a large, systemic 'shock'- Medicare Part D - on existing treatment patterns and outcomes. 3. Technological Growth and the Efficiency of Health Care Diffusion. We study the contribution of "high- tech" health care to cost growth, the diffusion of different types of medical innovations, whether high-quality health providers affect population-level health outcomes, and how provider networks affect diffusion. 4. Geography and Disparities in Health and Health Care. We propose hospital-level disparity "report cards," to study sorting of patients to disproportionately Black hospitals and to test whether the preferences of patients from a recent nation-wide survey of Medicare enrollees are reflected in their treatments. Finally, we estimate how racial differences in surgical rates affect disparities in actual health outcomes. 5. Norms Governing Physician Decision-Making For Critically III Elders. We use qualitative methods to describe the norms and values that influence the use of life-sustaining treatments among critically ill elders in emergency rooms and hospitals. We plan to test the feasibility of one or more interventions to change practice norms with the broader aim of improving efficiency. Cores: The Cores include an initiative to work with seven leading hospitals to address inefficiency in the provision of care, data support, and health efficiency measures for users of the Health and Retirement Study.